Vibratory tamper

Abstract

A compact and stable vibratory tamper of relatively low height comprises a crank case, a laterally mounted motor which is arranged to impart a linear reciprocating motion to an intermediate member via a planetary gear arrangement, a crankshaft, and a crank arm, and a tamping foot which is moved by the intermediate member by means of at least two oppositely acting springs which act between the intermediate member and the tamping foot and which overlap at least partially in the axial direction.

We claim: 
     
       1. In a vibratory tamper comprising a crank case, a motor unit laterally mounted on said crank case, a gear unit, a crankshaft driven by said motor unit through said gear unit, a movable intermediate member, a crank arm connecting said intermediate member to said crankshaft for reciprocation of said intermediate member, guide means for guiding said intermediate member linearly when said intermediate member is reciprocated, a movable tamping foot, and at least two oppositely acting springs mounted between said intermediate member and said tamping foot whereby motion is transmitted to said tamping foot from said intermediate member, the improvement wherein said gear unit is a planetary gear comprising an inner wheel, a hollow intermediate shaft connected to said crankshaft and having a hollow portion, means journalling said inner wheel in said hollow portion, an outer wheel rigidly attached to said crank case, and at least one intermediate planet wheel coupled to said intermediate shaft and engaging between said inner and outer wheels, said tamper including means drivingly connecting said motor unit to said inner wheel, and wherein said oppositely acting springs overlap at least partially in the axial direction. 
     
     
       2. A vibratory tamper as claimed in claim 1, wherein said oppositely acting springs are disposed alongside one another with respect to the direction of motion. 
     
     
       3. A vibratory tamper as claimed in claim 1, wherein said oppositely acting springs are disposed coaxially with one another. 
     
     
       4. A vibratory tamper as claimed in claim 2, wherein said oppositely acting springs comprise a plurality of outer springs and at least one inner spring, said outer springs being disposed in spaced-apart relationship around said inner spring, and said inner spring acting in opposition to said outer springs. 
     
     
       5. A vibratory tamper as claimed in claim 4, wherein said guide means comprises a plurality of guide rods and said movable tamping foot is mounted on said guide rods to guide said tamping foot in linear motion, said guide rods being disposed alternately with said outer springs concentrically about the axis of said inner spring. 
     
     
       6. A vibratory tamper as claimed in claim 4, wherein said guide means comprises a plurality of guide rods, and said outer springs are disposed coaxially about said guide rods. 
     
     
       7. A vibratory tamper as claimed in claim 5, wherein there are three of said guide rods and three of said outer springs. 
     
     
       8. A vibratory tamper as claimed in claim 6, wherein there are three of said guide rods and three of said outer springs. 
     
     
       9. A vibratory tamper as claimed in claim 5, wherein said intermediate member comprises an upper component, guide heads attached to said upper component and surrounding said guide rods, a lower component, and a connecting member connecting said upper component to said lower component, and wherein a cup-shaped spring support is attached to said tamping foot, said inner spring surrounding said connecting member and acting between said lower component and said cup-shaped spring support while said outer springs act between said tamping foot and said upper component. 
     
     
       10. A vibratory tamper as claimed in claim 9, wherein said guide rods are fixed with respect to said crank case and said guide heads are slidable on said guide rods, and said tamping foot is provided with guide sleeves which are also slidable on said guide rods. 
     
     
       11. A vibratory tamper as claimed in claim 1, wherein said crankshaft is mounted overhung in said crank case, and said crankshaft and said intermediate shaft are provided with interengaging means whereby said intermediate shaft is connected ina torsionally keyed manner to said crankshaft. 
     
     
       12. A vibratory tamper as claimed in claim 1, wherein said motor unit has a suspended cylinder. 
     
     
       13. A vibratory tamper as claimed in claim 1, including a height-adjustable guide fork attached to a said crank case.